We examined relationships between depressive rumination, anger rumination, and features of borderline personality disorder in a sample of 93 students with a wide range of borderline symptoms. All completed self-report measures of borderline features; trait-level negative affect; depressive and anger rumination; and current symptoms of depression, anxiety, and stress. Depressive and anger rumination were strongly associated with borderline features after controlling for comorbid symptoms of depression, anxiety, and stress. Both types of rumination showed significant incremental validity over trait-level sadness, anger, and general negative affect in predicting borderline features. Relationships with borderline features were stronger for anger rumination than for depressive rumination. Relationships between trait-level negative affect and borderline features were substantially reduced when anger rumination was included in regression models, suggesting the need for longitudinal analyses of mediation. Findings suggest that severity of borderline symptoms is influenced by ruminative thinking in response to negative affect, especially anger.